Many hardwired communications systems use plug and jack connectors to connect a communications cable to another communications cable or to a piece of equipment such as a computer, printer, server, switch or patch panel. By way of example, high speed communications systems routinely use such plug and jack connectors to connect computers, printers and other devices to local area networks and/or to external networks such as the Internet. FIG. 1 depicts a highly simplified example of such a hardwired high speed communications system that illustrates how plug and jack connectors may be used to interconnect a computer 11 to, for example, a network server 20.
As shown in FIG. 1, the computer 11 is connected by a cable 12 to a communications jack 15 that is mounted in a wall plate 19. The cable 12 is a patch cord that includes a communications plug 13, 14 at each end thereof. Typically, the cable 12 includes eight insulated conductors. As shown in FIG. 1, plug 14 is inserted into an opening or “plug aperture” 16 in the front side of the communications jack 15 so that the contacts or “plug blades” of communications plug 14 mate with respective contacts of the communications jack 15. If the cable 12 includes eight conductors, the communications plug 14 and the communications jack 15 will typically each have eight contacts. The communications jack 15 includes a wire connection assembly 17 at the back end thereof that receives a plurality of conductors (e.g., eight) from a second cable 18 that are individually pressed into slots in the wire connection assembly 17 to establish mechanical and electrical connections between each conductor of the second cable 18 and a respective one of a plurality of conductive paths through the communications jack 15. The other end of the second cable 18 is connected to a network server 20 which may be located, for example, in a telecommunications closet of a commercial office building. Communications plug 13 similarly is inserted into the plug aperture of a second communications jack (not pictured in FIG. 1) that is provided in the back of the computer 11. Thus, the patch cord 12, the cable 18 and the communications jack 15 provide a plurality of electrical paths between the computer 11 and the network server 20. These electrical paths may be used to communicate electrical information signals between the computer 11 and the network server 20. It will be appreciated that typically one or more patch panels or switches, along with additional communications cabling, would be included in the electrical path between the second communications cable 18 and the network server 20. However, for ease of description, these additional elements have been omitted from FIG. 1 and the second communications cable 18 is instead shown as being directly connected to the server 20.
In the above-described communications systems, the information signals are typically transmitted between devices over a pair of conductors (hereinafter a “differential pair” or simply a “pair”) rather than over a single conductor. The two conductors of each differential pair are typically twisted tightly together in the communications cables and patch cords, and thus each cable and patch cord includes four twisted differential pairs of conductors. As is known to those of skill in the art, the signals transmitted on each conductor of a differential pair have equal magnitudes, but opposite phases, and the information signal is embedded as the voltage difference between the signals carried on the two conductors of the pair. When signals are transmitted over a conductor (e.g., an insulated copper wire) in a communications cable, electrical noise from external sources may be picked up by the conductor, degrading the quality of the signal carried by the conductor. When the signal is transmitted over a twisted differential pair of conductors, each conductor in the differential pair often picks up approximately the same amount of noise from these external sources. Because approximately an equal amount of noise is added to the signals carried by both conductors of the twisted differential pair, the information signal is typically not disturbed, as the information signal is extracted by taking the difference of the signals carried on the two conductors of the differential pair, and this subtraction process may mostly cancel out the noise signal.
As shown in FIG. 1, a channel is formed between the computer 11 and the server 20 by cascading plugs, jacks and cable segments to provide connectivity between the two devices 11, 20. In this channel, the proximities and routings of the conductors and contacting structures within each plug-jack connection (e.g., where plug 14 mates with jack 15) can produce capacitive and/or inductive couplings. Moreover, since four differential pairs are usually bundled together in a single cable, additional capacitive and/or inductive coupling may occur between the differential pairs within each cable segment. These capacitive and inductive couplings in the connectors and cabling give rise to another type of noise that is called “crosstalk.”
In particular, “crosstalk” refers to unwanted signal energy that is induced onto the conductors of a first “victim” differential pair from a signal that is transmitted over a second “disturbing” differential pair. The induced crosstalk may include both near-end crosstalk (NEXT), which is the crosstalk measured at an input location corresponding to a source at the same location (i.e., crosstalk whose induced voltage signal travels in an opposite direction to that of an originating, disturbing signal in a different path), and far-end crosstalk (FEXT), which is the crosstalk measured at the output location corresponding to a source at the input location (i.e., crosstalk whose signal travels in the same direction as the disturbing signal in the different path). Both types of crosstalk comprise an undesirable noise signal that interferes with the information signal that is transmitted over the victim differential pair.
One method of reducing crosstalk in a communications system is to twist the conductors of each differential pair together at different rates that are not harmonically related. This technique typically ensures that each conductor in a cable picks up approximately equal amounts of signal energy from the two conductors of each of the other differential pairs included in the cable. While such twisting of the conductors and/or various other techniques may substantially reduce crosstalk in cables, most communications systems include communications connectors (i.e., jacks, plugs, connecting blocks, etc.) that interconnect the cables and/or connect the cables to computer hardware. Unfortunately, the connector configurations that were adopted years ago—and which still are in effect in order to maintain backwards compatibility—generally did not maintain the arrangement and geometry of the conductors of each differential pair so as to closely control the impedance of each pair or to minimize the crosstalk coupling between the differential pairs in the connector hardware. For example, pursuant to the TIA/EIA-568-B.2-1 standard approved Jun. 20, 2002 by the Telecommunications Industry Association, in the connection region where the blades of a modular plug mate with the contacts of the modular jack (referred to herein as the “plug-jack mating region”), the eight conductors 1-8 must be aligned in a row, with the eight conductors 1-8 arranged as four differential pairs specified as depicted in FIG. 2. As is apparent from FIG. 2, this arrangement of the eight conductors 1-8 will result in unequal coupling between the differential pairs, and hence both NEXT and FEXT is introduced in each connector in industry standardized communications systems.
The above-referenced TIA/EIA-568-B.2-1 standard requires compliance with interface specifications set forth in the FCC Part 68.500 document, which defines, among other things, the dimensions and configurations for various plug-jack interfaces, including plugs and jacks that conform to the Registered Jack 45 (“RJ-45”) wiring standard. Herein, a plug or jack that substantially complies with the RJ-45 wiring standard is referred to as an “RJ-45” plug or jack.
A wide variety of RJ-45 plugs are known in the art, including plugs that directly mount each conductor of the communications cable to a respective plug blade and plugs that terminate the conductors into a printed circuit board and use conductive traces on the printed circuit board to connect each conductor of the cable to a respective plug blade that is mounted on the printed circuit board. However, RJ-45 plugs having improved characteristics and/or performance are desired.